Telecommunications networks carry various types of information between users, e.g., voice, data, video. A typical telecommunications network includes many components or modules that work together to make a connection between users. For example, a telecommunications network typically includes switches, transport lines, terminals and other conventional equipment used to create connections between users.
Errors can occur in any one of these modules of the network. For example, a fiber optic cable that carries signals for the network can be cut inadvertently or otherwise damaged such that it cannot acceptably carry data. To prevent errors of this nature from hindering communications, networks include redundant components so that when a working component stops functioning acceptably, a replacement or protection component can be switched into the network in place of the working component. Thus, the network is able to continue to carry information despite errors. This is referred to in the industry as network survivability, of which protection switching is an example which uses dedicated protection components.
In recent years, the telecommunications industry has begun developing new networks that carry user traffic over virtual connections in the form of cells or fixed-length packets of data, e.g., asynchronous transfer mode (ATM) networks. Each cell contains a header that includes information as to the destination of the cell or packet. At each network element (NE), the cells are routed through its network modules to the destination endpoint based on the identifiers in the header of the cell. Thus, the same transmission medium can be shared by many contemporaneous connections which span different parts of the network. These cell-based, as opposed to traditional time-slot based, networks introduce new problems into the area of network survivability. The redundant routes in the network may carry traffic for different virtual connections along various portions of the routes. If care is not taken in deciding how to effectuate protection switching for the various virtual connections involved, system capacity and availability could be adversely affected by switching a virtual connection that is, in fact, not affected by the failure.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an improved system and method for protection switching in a network that uses virtual connections.